Emitter object shows up in reflection/transmission
I just added a light path node to the emitter material, with the Is Glossy Ray switching between emission and transparency, and got this.



Is this what you had in mind?

Edit: in case you'd ever want to control both Is Glossy Ray and Is Camera Ray from the shader instead of using the Ray Visibility tab in object properties, you can do that with a math node. Connect both Is Glossy Ray and Is Camera Ray to the math node via Add. Maximum also works. You will get zero only if both are zero, meaning you get visibility only if it's neither a camara ray nor a glossy ray, which is what we want.